In the prior art, as shown in FIG. 1, it is known to coat an insulating paste 11 on a ceramic substrate 10, dry the paste to evaporate the thinners, deposit a photosensitive resin 12 on the insulating layer, dry the layer 12, placed a patterned lithographic mask 13 over the surface, expose with UV through openings 14, develop and remove portions of the layers 12 and 11 and fire the assembly resulting in the structure of FIG. 1c. Such a teaching may be found in U.S. Pat. No. 4,119,480.
The present invention is directed to a process for complex, high density microcircuits in which thick film dielectric pastes are photolithography patterned into high resolution stencils to produce complementary conductor circuitry patterns, the voids of the developed dielectric stencil are filled with thick film conductor paste, and then there is a cofiring of the conductor and the dielectric. With this new process the number of separate firing operations is reduced. The reduction in the number of firings is important in multilevel hybrid structures because material interactions are reduced since they are related to the number of firings. Registration is maintained since it too is a function of number of firings. The dielectric stencil approach minimizes the conductor paste rheology contraints because the conductor paste is contained in the dielectric voids.